The polymer substrates of flexible solar cell (FSC) electrodes play a crucial role in determining the electrode performance as well as the device performance and reliability. However, most of the FSC electrode polymer substrates suffer from high coefficients of thermal expansion (CTE) and thermal instability when exposed to thermal-cycling impact. Here, a nanocellulose/epoxy hybrid substrate employing chemically modified cellulose nanofibers, demonstrating significantly improved thermal properties as well as high optical transparency, is presented. Benefiting from nanoscale morphology and surface functional groups of the cellulose nanofibers, which enable excellent compatibility and interfacial interaction with the epoxy matrix, the hybrid substrate’s thermal properties are significantly improved with a decreased CTE of 19 ppm/K, increased glass -transition temperature (T_g) of 71.8 °C, and increased half-life thermal decomposition temperature (T_d,50%) of 376 °C. Concurrently, mechanical properties are greatly enhanced with increases in ultimate strength and ultimate strain by 41 and 121.5%, respectively. In particular, the hybrid substrates maintained their high transmittance of 89%@600 nm and demonstrated no transparency loss after the introduction of cellulose nanofibers. Moreover, the conductive layer of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate deposited on the substrate retained a stable conductivity of around 835 S/cm without noticeable electrical degradation after withstanding the environmental thermal-cycling impact. With significantly improved thermal and mechanical properties as well as retained optical transparency and stable electrode conductivity, the use of this newly developed hybrid substrate may open opportunities for the fabrication of high-performance, low-cost FSCs.

中文翻译：

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高度透明，热稳定且机械坚固的混合纤维素-纳米纤维/聚合物基底，用于柔性太阳能电池的电极

柔性太阳能电池（FSC）电极的聚合物基板在确定电极性能以及器件性能和可靠性方面起着至关重要的作用。然而，当受到热循环冲击时，大多数FSC电极聚合物基材都具有高的热膨胀系数（CTE）和热不稳定性。在此，提出了一种使用化学改性的纤维素纳米纤维的纳米纤维素/环氧杂化底物，其显示出显着改善的热性能以及高光学透明性。得益于纤维素纳米纤维的纳米级形貌和表面官能团，它们具有出色的相容性和与环氧基质的界面相互作用，该杂化基材的热性能得到显着改善，CTE降低了19 ppm / K，T _g）为71.8°C，半衰期增加的热分解温度（T _d，50％）376°C。同时，机械性能大大提高，其极限强度和极限应变分别提高了41％和121.5％。特别地，在引入纤维素纳米纤维之后，杂化基底在600nm处保持其89％的高透射率并且没有显示出透明性损失。此外，沉积在基材上的聚（3,4-亚乙二氧基噻吩）：聚苯乙烯磺酸盐的导电层在经受环境热循环冲击后保持了约835 S / cm的稳定电导率，而没有明显的电降解。通过显着改善的热和机械性能以及保持的光学透明性和稳定的电极电导率，这种新开发的混合基板的使用可能为高性能，高品质的制造提供机会，